10A Stage (Road to STS-122/1E)

[MeteorWayne]

No, not really. A good examination confirming that it isn't worse than what was expected. For the SARJ joint, took more samples and parts to be returned for examinatuion. 2 of the 3 surfaces of the weight bearing ring look fine, it's just one of the 3 surfaces that have the problem. A few ideas floating around, but not enough data yet to find root cause.<br /><br />For the BGA, no visible problem found, will be sending up possible parts in next shuttles.<br />Testing took place with some cables disconnected while they went to the SARJ, then reconnected afterward. <br /><br />Much analysis required before deciding on a next step.<br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[bobw]

They think the problem with the BGA is in the motor.<br /><br />For the SARJ it sounds like they think the pre-load on the bearings may be too high. Said there was a minimum but no maximum in the specs. They were talking about the stress of the pre-load compressing the material under the nitride heat treated layer causing the hardened surface to crack. It didn't sound like they think something is scraping while the joint rotates. In the end, though, they still don't know the root cause.<br /><br />They really want Dan Tani up there to work on the BGA, may keep him there till spring. New bearings (edit: for the SARJ) weigh 20 pounds each and 12 of them won't fit on the next trip for the Shuttle.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[erioladastra]

"will be sending up possible parts in next shuttles."<br /><br />to be clear, the replacement BMRRM is already on orbit in PMA3.

 

[Testing]

See the thread Disturbing about the ISS. That race is TOAST. Long term use is out of the question. I call that surface spalling and it will not go away or be cleaned up. Look at the size of mag particles stuck to the trundle housing on the right. <div class="Discussion_UserSignature"> </div>

 

[bobw]

Yes, the pictures at Comga's link really make everything clear. I was seriously confused when Dan Tani said it looks like a "coating" on the race ring looks pitted, abraded, sandpapery. (11/24/07 spacewalk) The whole surface is flaking away. <div class="Discussion_UserSignature"> </div>

 

[bobblebob]

Wow, never seen the damage that close up before. That really does not look good at all

 

[larper]

What I still don't understand is, what are they talking about replacing to solve the problem? The structure itself looks damaged. It doesn't look like replacing the rollers solves anything. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[MeteorWayne]

That is not what they plan to replace, if anything.<br /><br />Everyone really need to pay attention all during the process, as many posts here are far more dire than what the ISS team considers it to be.<br /><br />The suggestion is that the coating of the raceway is fracturing due to cracks below.<br /><br />They thing that POSSIBLY by replacing the trundle bearings with different loads, the stress will be reduced. That might not help this surface, but might allow the backup surfaces to be just fine.<br />In the meantime, they BELIEVE it might be possible to live with this condition, and still rotate the joint (less often than optimum, but enough to supply required power) on the current race.<br />The idea is to put off the transfer to the unused backup raceway as long as possible, to allow as much analysis, planning, and repiar to take place before that time.<br /><br />Geez, everyone seems to think this is a disaster of mega proportions. That is not the feeling I got from the ISS team...what I get is "it's another day on the space station, dealing with whatever comes up"<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[larper]

I am not being alarmist. I am just trying to understand where the backup raceway lives. I see only two gears: one on the stationary side, and one on the rotating side. The damage seems to be on one of the gears. I don't understand how there can be a backup to this. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[MeteorWayne]

You are misunderstanding the image.<br />All raceways in use are on the left side of the image. Only one (the one with the problem) is visible, the other 2 were checked and are fine.<br /><br />On the images displayed, the raceways in use are the ones on the left; with the surface "problems".<br /><br />The ones (only 1 of the 3 surfaces are visible) on the right have had no forces or contact applied to it. It's a backup.<br /><br />If needed, the entire assembly gets shoved to the right, and the surfaces on the right are used. They want to delay that move as long as possible, while they understand the problem on the left view raceways. <br /><br />Edit for clarity. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[larper]

I don't see how you can interpret this as not being on the gears. Certainly not the teeth of the gears, but the gear none-the-less.<br /><br />http://collectspace.com/review/iss16_sarjinspect03-lg.jpg <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[larper]

Gods, I wish we could post pictures again.<br /><br />I see two sets of teeth. These teeth are separated by a large space. To the right of the teeth on the right seems to be a track, I guess that is the race. That track is all messed up. This track seems to be physically on the same structure as the teeth, so I called that a gear. To replace the race would be also replacing the teeth.<br /><br />Now, if the set of teeth on the left is some sort of backup hardware, I don't see it. There is no race associated with those teeth, and that entire assembly is not free to move anyway. It is on the "fixed" side of the SARJ. <br /><br />I simply don't get where the other race is, and how they would switch to it. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[erioladastra]

"That race is TOAST. "<br /><br />No, that is far from certain. It might well be perfectly useable - the question is what is causing the damage and can we fix it.

 

[bobw]

<font color="yellow">Gods, I wish we could post pictures again. </font><br /><br />I feel your pain.<br /><br />In that picture (iss16_sarjinspect03-lg.jpg) the right slanted race is cruddy. There are three races on that bull gear: the cruddy slanted one, one on the other side of the gear teeth perpendicular to them, and one on the back. The gear is clamped on three sides. This link has some nice pictures toward the end.<br /><br />http://www.space.gc.ca/asc/pdf/2000_BOUCHER.PDF<br /><br />The other gear has the same races but it is installed as a mirror image, so the perpendicular side is visible and the slanted side is on the other side of the teeth. I have heard that to use the other gear it is necessary to flip the bearings so they engage the other gear on three sides. That means the trundle bearing gets bolted to the outboard gear.<br /><br />Here's the part that gets confusing for me and I'm really not sure <img src="/images/icons/laugh.gif" /><br /><br />If the power for the drive motors comes through the Utility Transfer Assembly in the central hub then if the motors are attatched to the outboard part but run the inboard gear the whole outboard part would still rotate but the motors and trundle bearings would rotate too.<br /><br />It seems like the only way to use the inboard gear to run the outboard part without spinning the outboard gear would be if there is a sliding spline that could couple power to a shaft in the center and the inboard gear isn't really permanently stationary at all.<br /><br />Darned if I can figgure it out, but it doesn't really make sense to put teeth on the inboard gear if you can't hook a motor to it, does it? <br /><br />For what it's worth you can guess how hard I've been looking for answers when I start clicking on stuff like <i>"Mechanically Induced g-Jitter from Space Station Rotary Joints"</i> looking for blueprints <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[thereiwas]

Given that all the power from the arrays has to come in thru the rotating joint, sending a small amount out to the motors should not be difficult.

 

[bobblebob]

This was from the article posted in the other thread:<br /><br />"Repairs to the damaged solar rotary joint, on the other hand, will be a massive effort requiring as many as four spacewalks and likely will not be attempted until next fall, Suffredini said"<br /><br />Kibo is going up before next fall arent it? So does that mean its certain to be delayed as they need the SARJ working to support Kibo? <br /><br />Even if its not, to attempt a 4 EVA repair mission would mean cancelling other tasks, which would delay the program

 

[erioladastra]

<br />Updates:<br /><br />- EVA to repair the BMRRM will now be Jan 30<br />- There might be some SARJ work on that EVA but still TBD. Focus is now on the lubrication breaking down and needing to be reapplied. TBAs are off 1 J/A and no switch to the other ring likely before ULF-2 if at all.<br />- As in other thread, 1E will be around Feb 7

 

[bobblebob]

How big a job is it to switch gear/race? Would it be feasible to switch it over until they can work out a fix for the damaged race and then switch back again if needs be? At least then they can get some use out of the SARJ

 

[bobblebob]

Fair enough, didnt know it took that many EVA's to switch it. Can understand why Nasa dont want to do that unless they have no other option